1. Field of the Invention
The present invention relates to a shift switch control device for selection lever units of automatic transmissions and, more particularly, to a shift switch control device for selection lever units of sport mode-type automatic transmissions capable of selectively performing an automatic transmission mode or a manual transmission mode as desired, the shift switch control device designed to accomplish a reliable up-shift operation, so-called a xe2x80x9c+xe2x80x9d shift operation, and a reliable down-shift operation, so-called a xe2x80x9cxe2x88x92xe2x80x9d shift operation, during a manual transmission mode, and to be reduced in the number of its parts, thus being preferably simplified in its construction.
2. Description of the Prior Art
In recent years, sport mode-type automatic transmissions, designed to allow drivers to select an automatic transmission mode or a manual transmission mode as desired in accordance with driving conditions and/or driver""s tastes while driving, have been developed and proposed to be equipped within, particularly, a variety of expensive luxury cars.
Different from conventional transmissions with a fixed automatic transmission mode or a fixed manual transmission mode, such sport mode-type automatic transmissions allow drivers to enjoy the driving feeling to the full while selecting the automatic transmission mode or the manual transmission mode as desired in accordance with driving conditions and/or their tastes while driving their cars.
Such a sport mode-type automatic transmission is provided with a selection lever unit for allowing a driver to perform a desired shifting operation. The construction of a conventional selection lever unit for such sport mode-type automatic transmissions is shown in FIGS. 7, 8 and 9. As shown in the drawings, the conventional selection lever unit has a selection lever 100, which is installed within a main frame 111 and is used for selecting a desired mode or a desired range within a transmission pattern 110 having a manual transmission mode and an automatic transmission mode. A cable bracket 113 is connected to a shift cable (not shown) at a position around the selection lever 100. The above cable bracket 113 is operated in conjunction with the selection lever 100 when the automatic transmission mode is selected, thus actuating a transmission manual valve (not shown).
The selection lever 100 has two connection protrusions 114, while the cable bracket 113 has a connection lever 115 at a position corresponding to the connection protrusions 114. Therefore, the selection lever 100 is operated in conjunction with the cable bracket 113 through the engagement of the two connection protrusions 114 and 114xe2x80x2 with the connection lever 115 during an automatic transmission mode.
The conventional selection lever unit has a shift switch control device of FIG. 9. As shown in the drawing, the conventional shift switch control device for selection lever units comprises a manual mode select switch 103, an up-shift switch 101, a down-shift switch 102 and a switch actuation unit, which are provided on the top wall of the main frame 111. The up-shift switch 101 and the down-shift switch 102 are used for performing the up- and down-shifting operations when the manual transmission mode is selected by the selection lever 100.
In such a case, the up-shift switch 101 is positioned at the front portion of the shift switch control device, while the down-shift switch 102 is positioned at the rear portion of the control device. In addition, the manual mode select switch 103 is positioned between the up-shift switch 101 and the down-shift switch 102.
Two shift switch actuation members 104 and 105 are provided at positions corresponding to the up-shift switch 101 and the down-shift switch 102, with a gap defined between the two shift switch actuation members 104 and 105. When the manual transmission mode is selected by the selection lever 100, the lever 100 is inserted into the gap defined between the two shift switch actuation members 104 and 105 while pushing and turning on the manual mode select switch 103.
In each of the two shift switch actuation members 104 and 105, a tipping bar 108 is set within a housing 106 while being normally biased by a return spring 107 at its rear end, thus normally positioning the selection lever 100 at a neutral position.
Therefore, when the selection lever 100 is moved to perform a desired shifting operation, the tipping bars 108 of the two shift switch actuation members 104 and 105 actuate the up and down-shift switches 101 and 102, thus allowing the switches 101 and 102 to output up- and down-shifting signals.
In such a case, the manual mode select switch 103 is continuously operated by a side surface of the selection lever 100, thus being maintained at its activated state.
However, such a conventional shift switch control device for selection lever units of automatic transmissions is problematic in that it is very difficult to maintain the precise actuation gaps between the tipping bars 108 and the up- and down-shift switches 101 and 102. In addition, the operational direction of the tipping bars 108 is different from the operational direction of the up- and down-shift switches 101 and 102. Therefore, the shift switch control device may fail to accomplish a desired operational reliability.
In addition, it is very difficult to manufacture the tipping bars, and so the tipping bars are very expensive. Another problem experienced in the conventional shift switch control device resides in that it has a complex construction and is not easy to install within a limited area.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a shift switch control device for selection lever units of automatic transmissions capable of selectively performing an automatic transmission mode or a manual transmission mode as desired, which is designed to accomplish a reliable up-shift operation, so-called a xe2x80x9c+xe2x80x9d. shift operation, and a reliable down-shift operation, so-called a xe2x80x9cxe2x88x92xe2x80x9d shift operation, during a manual transmission mode, and which is reduced in the number of its parts, thus being preferably simplified in its construction.
In order to accomplish the above object, the present invention provides a shift switch control device for selection lever units of automatic transmissions, comprising: a selection lever installed within a main frame of a chassis by a hinge shaft and used for selecting a desired range within a transmission pattern during an automatic transmission mode and performing an up- or down-shifting operation during a manual transmission mode, the transmission pattern having an automatic transmission mode pattern and a manual transmission mode pattern, the selection lever turning on or off up- and down-shift switches during the manual transmission mode, thus performing the up- or down-shifting operation, the up- and down-shift switches being mounted to the chassis by brackets such that the up- and down-shift switches are symmetrical along a central axis of a M-stage of the manual transmission mode pattern; a rotary lever mounted to the hinge shaft at its lower end at one side of the selection lever such that the top portion of the rotary lever is positioned in a gap between the up- and down-shift switches, with a key slot formed at the central portion of the rotary lever at a surface facing the selection lever; a rotary lever return means provided at the lower end of the rotary lever for providing a forward and backward returning force to the rotary lever; a locking key hinged within a casing of the selection lever such that the locking key is rotatable to pass through a connection hole of the casing so as to be finally inserted into the key slot of the rotary lever, thus locking the rotary lever to the selection lever at the M-stage of the manual transmission mode pattern, the locking key being normally biased by a key return spring in a direction such that the locking key is inserted into the key slot of the rotary lever; and a key actuation rod set within the casing of the selection lever, with a keyhole having a size corresponding to the radius of actuation of the locking key and formed at one sidewall of the key actuation rod, and a knob mounted to a top end of the key actuation rod and provided with a push button, the key actuation rod being operated in conjunction with both the push button and the key return spring, thus rotating the locking key to the outside or inside of the casing of the selection lever.
In the above shift switch control device, the M-stage of the manual transmission mode pattern has a plus (+) stage for actuating the up-shift switch and a minus (xe2x88x92) stage for actuating the down-shift switch.
The rotary lever return means comprises: front and rear support brackets mounted to the chassis at positions in front and back of the rotary lever; and a return spring positioned between the rotary lever and each of the front and rear support brackets.
In addition, the key return spring is mounted to the hinge shaft of the locking key, with opposite ends of the key return spring supported by a pin of the locking key and a pin of the casing of the selection lever.
The keyhole of the key actuation rod has a key inlet opening at one side thereof, thus allowing the locking key to be inserted into the keyhole after passing through the key inlet opening, with a key actuation pin provided at a top edge of the key inlet opening for pushing the locking key into the casing of the selection lever when the key actuation rod is moved downward.